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Wiring Schemes

Wiring for telephone and data networks should be installed using standardized wiring schemes that are developed and maintained by the Electronic Industries Alliance and the Telecommunications Industry Association (EIA/TIA). Following the wiring guidelines contained in these codified standards will ensure that wire and cabling systems work properly with all standardized equipment and will aide in the future testing and repair of these systems.

We are including here a brief introduction to standardized wiring schemes for telco wiring and the most common data networks. This information applies to about 90% of all current voice and data networks in existence.

Telco Wiring

The basic (and out dated) wire used to connect telephones is called station wire (aka "quad or JK") and is suitable only for standard voice telephone systems. It is made of four conductors that are not twisted pairs inside a protective jacket. The standard colors for these conductors is red, green, yellow, and black. This type cable is not commonly used today, it is included because you will frequently encounter it in older buildings.

      • 1st pair-Green ("tip") & Red ("ring")
      • 2nd pair- Black ("tip") & Yellow ("ring")
The wires are paired green-red for pair 1 and black-yellow for pair 2. The "Tip and Ring" is used to designate the polarity of the circuit; with Tip being the positive and Ring being negative.

You can test for proper polarity with a test meter by placing the positive (usually red) lead on the Tip terminal (green or black wire) and the negative (usually black) lead on the Ring terminal (red or yellow wire) at any convenient junction box. The test meter should read a positive 48 volts DC if all phones are hung up or disconnected and about 10 volts DC if a phone is off hook during the test. WARNING!-When the phone rings their is 90 volts AC present on the line, and it can really give you a jolt, so be careful.

Category Wiring
Today every phone circuit is a potential data connection for such things as internet access and data transfer by modem. New and improved wire has been developed to handle the higher demands placed on it by such devices.

The wire used today for voice and data networks is called "Category" (CAT) wire. Cable categories are determined by its performance characteristics with lower Cat numbers such as Cat 3 having lower performance and higher Cat numbers higher performance. Cat 3 wire is currently used for voice and limited data transfer using a modem. Cat 5 is the industry standard for local area networks (LAN) that connect computers in most businesses.

This new wire uses a different and somewhat more complicated color scheme than station wire and is based on a primary color and a secondary color. The primary colors are white, red, black, yellow, violet, and the secondary colors are blue, orange, green, brown, slate. In this newer scheme; the "tip" wire is the primary color with marks of the secondary color (i.e., white with blue marks) and the "ring" wire is the secondary color, with marks of the primary color (i.e., blue with white marks).

Wire pairs are marked in groups of five. Each pair within a group uses the same primary color and a different secondary color; each group uses a different primary color. This allows identification of up to 25 pairs without duplication. This is likely to be the largest cable you will ever encounter in most residential or business environments.

Standard 4-Pair Wiring
Color codes
Pair 1T
Pair 2T
Pair 3T
Pair 4T

Cat 5 wire cables with four pairs are used extensively for most residential and office installations today. This cable has 8 conductors that are twisted into 4 pairs, it comes with and without a shield and is commonly referred to as Unshielded or Shielded Twisted Pair (UTP & STP for short) cable. The four pairs are colored blue, orange, green, and brown for pairs 1 through 4 respectively. This wire is used for multi-line telephone and ethernet LAN applications in both residential and business premises.

Wiring Modular Plugs and Jacks
When using Cat 5 wire for data applications virtually all connections are made with modular plugs and jacks. This modular equipment is made for a multitude of different applications and they all are physically similar; however, their internal wiring is specific to each application. The following charts and diagrams should help to visualize the various wiring methods.

Category 5 wiring standards:
EIA/TIA 568A/568B and AT&T 258A define the wiring standards and define two different wiring color codes.

Pin # EIA/TIA 568A AT&T 258A
Ethernet 10BASE-T Token Ring
1 White/Green White/Orange X  
2 Green/White Orange/White X  
3 White/Orange White/Green X X
4 Blue/White Blue/White   X
5 White/Blue White/Blue   X
6 Orange/White Green/White X X
7 White/Brown White/Brown    
8 Brown/White Brown/White    

Modular jacks have internal pigtail leads that connect to their contacts. This diagram shows the most common wiring color scheme used for these devices.

Jack Lead Colors
Pin #Jack Type
8P8C Keyed
1Blue (L)White (W)Orange (O)
2Orange (O)Black (B)Green (G)
3Black (B)Red (R)Red (R)
4Red (R)Green (G)Yellow (Y)
5Green (G)Yellow (Y)Black (B)
6Yellow (Y)Blue (L)Brown (N)
7Brown (N)--
8White (W)--

The Ubiquitous RJ31X Jack

The Federal Communications Commission regulations state that every electronic device that attaches to the telephone network is required to have a Registered Jack (RJ) as the means of connection. The RJ allows the device to be disconnected quickly from the telephone circuit if a problem develops on the line.

The RJ31X modular jack is the proper RJ to use for connecting alarm signaling devices to the telephone network. This RJ is special because it is a serial device. This means that devices connected with a RJ31X are inserted into the circuit rather than simply tapped onto the circuit. Since all life safety and most security alarm signaling devices require that the device be wired into the telephone circuit ahead of all other equipment so that it can capture the line during signal transmission, a serial device is required.

Another unique feature of this modular jack is the 8 position plug used to connect devices. The plug is wired to the alarm signaling device and upon insertion into the jack the signaling device is connected to the telephone circuit ahead of other equipment. With the plug inserted the circuit passes through the alarm signaling device; when the plug is removed the alarm signaling device is, of course disconnected and the circuit remains connected to the other devices on the line.

To correctly install a RJ31X jack the incoming telco network line is wired to the RJ31X jack first and then to other equipment (house phones etc.) as required. The following diagram depicts the correct way to install the RJ31X jack. Notice the shorting bars that allow a device to be inserted into the circuit. Also note that for this application only 4 of the 8 positions are used.

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